The invention relates to an occupant restraint system for motor vehicles having a gas bag or airbag. When not in use, the airbag is accommodated collapsed in a housing-like accommodation space. In the event of an accident to the motor vehicle, the airbag is automatically inflated by means of a gas generator to form an absorption cushion protecting the occupant, in the clearance between the accommodation space and occupant, with the gas bag expanding with a comparatively slow expansion rate towards the occupant, that is to say in the axial direction, and with a comparatively high expansion rate in the lateral direction.
Gas bag systems have for some time now been standard fittings in motor vehicles and have proven their worth.
As regards a reliable effectiveness of the gas bag, comparatively short inflation times must be guaranteed in order to ensure that the gas bag has already been inflated to form an absorption cushion before the occupant is flung towards the cushion in the event of an accident.
Although in general the short inflation time does not pose any safety problem for the occupant, in special cases injuries--even if comparatively harmless--can occur to the occupant, for example if, at the instant of ignition of the gas generator and the beginning of the inflation process, the occupant assumes a position closely in front of the accommodation space of the airbag. This can take place for example because the occupant has bent forwards. Furthermore, there is in principle the possibility in an accident that the vehicle undergoes at first a relatively slight impact which does not yet lead to the ignition of the gas generator but nevertheless allows the occupant, possibly without a safety belt, to slip or slide towards the accommodation space of the airbag. If the gas generator is then ignited in a subsequent, more intense impact, the occupant is already within the space provided for the inflated airbag, that is to say the explosively expanding airbag strikes comparatively violently against the occupant.
In order to reduce this problem, it is known in principle from U.S. Pat. Nos. 4,903,986; 5,004,266 and 5,009,452, to arrange the airbag such that it at first expands preferentially in the lateral direction.
In the case of U.S. Pat. No. 4,903,986, it is provided to this end to arrange the airbag below a specially designed cover which first tears open laterally and thus permits an immediate lateral expansion of the airbag whilst an expansion towards the occupant is at first prevented or delayed until the covering tears open completely.
According to U.S. Pat. No. 5,004,266, it is provided to secure the central airbag region, which attempts to expand towards the passenger, by means of a tear strip made of spring steel and, correspondingly, to permit only a delayed expansion of this airbag region.
U.S. Pat. No. 5,009,452 provides for there to be arranged, within the collapsed airbag, a plate which is mounted on stationary parts of the accommodation space and with which the central airbag region is releasably clamped, so that on ignition of the gas generator the lateral airbag regions are at first inflated.
In German Patent 38 18 185 it is disclosed to retard the expansion of a airbag during inflation by means of tear seams; by means of which the pleats in the airbag sleeve are at first held together.
German Patent Document DOS 35 44 704 shows an airbag which, in the collapsed state, is folded such that, on ignition of the airbag, at first the central bag region is inflated in order to force open a cover protecting the folded-up airbag.
German Patent Document DOS 37 07 370 discloses closing off the accommodation space serving to accommodate the airbag and to receive the gas generator, on its side facing the occupant, by means of a cover which, on ignition of the gas generator, is torn open by the expanding airbag reproducibly at a predetermined rupture point which, in plan view, is essentially H-shaped.
A similar arrangement is also disclosed in German Patent Document DOS 41 15 884. In order to increase the mobility of the cover parts which are movable after tearing open the predetermined rupture point, it is also provided to design the lateral cover regions with especially thin walls.
An object of the invention is to provide an advantageous design with which, in an especially simple manner, different expansion rates of the airbag in the axial and lateral direction can be ensured.
This object is achieved according to the invention in that lateral airbag regions are folded in a zigzag-shaped manner and central airbag regions are folded so as to be self-retarding, by the fact that these airbag regions expanding in the axial direction are provided with tear seams and/or the fold layers of these airbag regions expanding in the axial direction are tucked into one another.
The measures provided according to the invention can be readily carried out within the scope of the work sewing and folding up--which is necessary in any case in the production of the airbag sleeve.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.